Cerulean Warbler

Setophaga cerulea

The sky-blue upperparts of the male Cerulean Warbler are difficult to observe in summer: At that season, the birds stay high in the tops of leafy trees in the eastern United States and extreme southern Canada. The bird itself has become harder to observe in recent decades, as its numbers have decreased in parts of its range. Cowbirds, which lay their eggs in the warblers' nests, may be finding their unwitting "hosts" more easily as forest patches become smaller.

Conservation status

Possibly threatened or endangered. Surveys show strongly declining numbers in recent years. Nesting efforts may fail because of increasing cowbird parasitism in smaller patches of forest. May also be losing wintering habitat in tropics.

Deciduous forests, especially in river valleys. Breeds in mature hardwoods either in uplands or along streams. Prefers elm, soft maple, oak, birch, hickory, beech, basswood, linden, sycamore, or black ash. Nests only in tall forest with clear understory. In winter in tropics, found mostly in forest and woodland borders in foothills and lower slopes.

The sky-blue upperparts of the male Cerulean Warbler are difficult to observe in summer: At that season, the birds stay high in the tops of leafy trees in the eastern United States and extreme southern Canada. The bird itself has become harder to observe in recent decades, as its numbers have decreased in parts of its range. Cowbirds, which lay their eggs in the warblers' nests, may be finding their unwitting "hosts" more easily as forest patches become smaller.

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Feeding Behavior

Forages mostly high in trees, moving rapidly from limb to limb, searching among foliage and twigs for insects. Also flies out to catch flying insects in mid-air. In winter in the tropics, scattered individuals forage with mixed flocks, ranging from low to high in the trees.

Eggs

3-5, usually 4. Gray or creamy off-white, with spots of brown. Incubation by female only, probably 12-13 days. Apparently does not often host cowbird eggs where it can nest in unbroken mature forest, but may be parasitized more frequently in forest fragments. Young: Both parents feed the nestlings. Age at which the young leave the nest is not well known.

Young

Both parents feed the nestlings. Age at which the young leave the nest is not well known.

Diet

Insects. The diet is not well known; undoubtedly feeds mostly or entirely on insects, like most warblers. Has been observed feeding on caterpillars.

Nesting

Males arrive on breeding grounds near the middle of May. Nesting behavior has been little studied, owing to the difficulty of observing the nests. Nest: Placed on horizontal branch of hardwood, far from trunk and usually high, 15-90' up in tree. Favors oak, maple, basswood, elm, hickory, sycamore, beech, or tulip trees. Nest is a small, shallow open cup (probably built by female), made of bark strips, grasses, weeds, spider silk, and lichen; lined with moss and hair.

Migration

Moves south relatively early in fall. Spring migrants coming north from South America may make a regular stopover in Belize before continuing north across the Gulf of Mexico to southeastern United States. A very rare stray anywhere in west.

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Migration

Moves south relatively early in fall. Spring migrants coming north from South America may make a regular stopover in Belize before continuing north across the Gulf of Mexico to southeastern United States. A very rare stray anywhere in west.

How climate change could affect this bird's range

In the broadest and most detailed study of its kind, Audubon scientists have used hundreds of thousands of citizen-science observations and sophisticated climate models to predict how birds in the U.S. and Canada will react to climate change.

Cerulean Warbler

Each map is a visual guide to where a particular bird species may find the climate conditions it needs to survive in the future. We call this the bird’s “climatic range.”

The colors indicate the season in which the bird may find suitable conditions— blue for winter, yellow for summer (breeding), and green for where they overlap (indicating their presence year-round).

The darker the shaded area, the more likely it is the bird species will find suitable climate conditions to survive there.

The outline of the approximate current range for each season remains fixed in each frame, allowing you to compare how the range will expand, contract, or shift in the future.

The first frame of the animation shows where the bird can find a suitable climate today (based on data from 2000). The next three frames predict where this bird’s suitable climate may shift in the future—one frame each for 2020, 2050, and 2080.

You can play or pause the animation with the orange button in the lower left, or select an individual frame to study by clicking on its year.

The darker the color, the more favorable the climate conditions are for survival. The outlined areas represent approximate current range for each season. More on reading these maps.